Imaging lens composed of five optical elements

ABSTRACT

An imaging lens comprises five optical elements, in order from an object side to an image side, comprising, a first lens as a first optical element having positive refractive power, a second lens as a second optical element having negative refractive power and a convex surface facing the object side near an optical axis, a third lens as a third optical element having the refractive power, and a fourth lens as a fourth optical element having refractive power and the convex surface facing the object surface near the optical axis, wherein and an aberration correction optical element as a fifth optical element are arranged between said third lens and said fourth lens, said aberration correction optical element has both flat surfaces near the optical axis and aspheric surfaces.

The present application is based on and claims priority of Japanesepatent applications No. 2017-073758 filed on Apr. 3, 2017, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an imaging lens which forms an image ofan object on a solid-state image sensor such as a CCD sensor or a C-MOSsensor used in a compact imaging device, and more particularly to animaging lens which is built in an imaging device mounted in anincreasingly compact and low-profile smartphone and mobile phone, aninformation terminal such as a PDA (Personal Digital Assistant), a gameconsole, PC and a robot, moreover, a home appliance and an automobilewith the camera function.

Description of the Related Art

In recent years, it becomes common that camera function is mounted inmuch information equipment. Furthermore, it becomes indispensable as anadditional value of products to mount a camera in the mobile phone andthe smartphone, and the terminal equipment such as the PDA. Not only themobile terminal equipment, but demand of products with the camerafunction such as a wearable appliance, the game console, the PC, thehome appliance and a drone is more increased, and development ofproducts will be rapidly made accordingly.

Corresponding to being compact and increasing in the number of pixels,the imaging lens is also required to have high performance in resolutionand image quality, and therefore spread thereof and reduction in costare also requested.

In order to meet demand of high performance, the imaging lens composedof a plurality of lenses becomes popular. There is also proposed theimaging lens composed of five lenses which enables high performance incomparison with the imaging lens composed of three or four lenses.

As a conventional imaging lens aiming the high performance, for example,imaging lenses disclosed in the following Patent Documents 1 and 2 areknown.

Patent Document 1 (JP2010-271541A) discloses an imaging lens comprisingin order from an object side, a first lens being a biconvex lens andhaving positive refractive power and, a second lens having negativerefractive power and a concave surface facing an image side, a thirdlens as a meniscus lens having positive refractive power and a convexsurface facing the image side, and a fourth lens as a double-sidedaspheric lens having negative refractive power and a concave surfacefacing the image side.

Patent Document 2 (U.S. Pat. No. 8,395,851) discloses an imaging lenscomprising in order from an object side, a first lens having positiverefractive power, an aperture stop, a second lens having negativerefractive power, a third lens having convex surfaces facing the objectside and an image side, a fourth lens having a meniscus shape having aconcave surface facing the object side, and a fifth lens having aconcave surface facing the image side. Thus configured, the imaging lensaims high performance.

SUMMARY OF THE INVENTION

The imaging lens disclosed in the above Patent Document 1 aims the highperformance using a small number of lenses, such as four, however fourlenses is not enough for aberration correction. Therefore, it isdifficult to respond to the demand of high pixel in recent year.

The imaging lens disclosed in the above Patent Document 2 is a lenssystem which is composed of five lenses, has a large diameter and iscompact and is in high performance, and is configured to largely reducemanufacturing cost. This lens system certainly achieves brightness ofF2.6. The lens configuration of the Patent Document 2, however, has aproblem that a ratio of total track length to focal length of an overalloptical system becomes too large.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problems, andan object of the present invention is to provide an imaging lens whichtelephoto ratio, a ratio of the total track length to focal length of anoverall optical system applicable to the above mobile terminal equipmentand information equipment is reduced, and which properly correctsaberrations and has high resolution.

In the present invention, classification of lens in optical elements ismade if the optical element has refractive power near an optical axis.The optical element having the refractive power near an optical axis iscalled as the lens. The optical element having no refractive power nearan optical axis does not change the focal length of an overall opticalsystem, and contributes to improvement of aberrations in a peripheralarea by effect of aspheric surfaces. This is called an aberrationcorrection optical element. Regarding terms used in the presentinvention, a convex surface, a concave surface or a flat surface of ashape of the lens surface implies a shape near the optical axis(paraxial portion). Positive or negative of the refractive power alsoimplies the refractive power near the optical axis (paraxial portion).The pole point made on the aspheric surface implies an off-axial pointon an aspheric surface at which a tangential plane intersects theoptical axis perpendicularly. The total track length is defined as adistance along the optical axis from an object-side surface of anoptical element arranged closest to the object side to the image plane.When measurement of total track length is made, thickness of an IR cutfilter or a cover glass which may be arranged between the opticalelement arranged closest to the image side and the image sensor isregarded as an air.

An imaging lens according to the present invention which forms an imageof an object on a solid-state image sensor, comprises five opticalelements, namely, in order from an object side to an image side, a firstlens as a first optical element having positive refractive power, asecond lens as a second optical element having negative refractive powerand a convex surface facing the object side near an optical axis, athird lens as a third optical element having the refractive power, and afourth lens as a fourth optical element having refractive power and theconvex surface facing the object surface near the optical axis, and anaberration correction optical element as a fifth optical element havingflat and aspheric surfaces facing both sides near the optical axis isarranged between the third lens and the fourth lens.

The imaging lens according to the above configuration achieveslow-profileness by strengthening the refractive power of the first lens,and properly corrects spherical aberration and chromatic aberration bythe second lens. The third lens maintains the low-profileness andcorrects coma aberration and field curvature. The fourth lens suitablycorrects the field curvature by the convex surface facing the objectside near the optical axis. The aberration correction optical element asthe fifth optical element properly corrects aberrations in a peripheralarea of an image by the aspherical shape formed on both sides.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (1) issatisfied:0.55<TTL/f<1.00  (1)wheref: focal length of the overall optical system, andTTL: distance along an optical axis from an object-side surface of thefirst lens to an image plane.

The conditional expression (1) defines a distance along the optical axisfrom the object-side surface of the first lens to an image plane to thefocal length of the overall optical system of the imaging lens, and is acondition for shortening total track length. When a value is below theupper limit of the conditional expression (1), the total track lengthcan be shortened and achieving compact size is facilitated. On the otherhand, when the value is above the lower limit, correction of fieldcurvature and axial chromatic aberration is facilitated and properoptical performance can be maintained.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (2) issatisfied:2.00<(d3/TTL)×100<12.65  (2)

-   where-   TTL: distance along an optical axis from an object-side surface of    the first lens to an image plane, and-   d3: thickness on the optical axis of the third lens.

The conditional expression (2) defines an appropriate scope of thicknesson the optical axis of the third lens, and is a condition for properlykeeping formability of the third lens and maintaining thelow-profileness. When a value is below the upper limit of theconditional expression (2), the thickness on the optical axis of thethird lens is prevented from being excessively large, and securing airspace on the object side and the image side of the third lens isfacilitated. As a result, low-profileness can be maintained. On theother hand, when the value is above the lower limit of the conditionalexpression (2), the thickness on the optical axis of the third lens isprevented from being excessively small, formability of the lens can beproperly kept.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (3) issatisfied:2.00<(d4/TTL)×100<7.10  (3)

-   where-   TTL: distance along an optical axis from an object-side surface of    the first lens to an image plane, and-   d4: thickness on the optical axis of the fourth lens.

The conditional expression (3) defines an appropriate scope of thicknesson the optical axis of the fourth lens, and is a condition for properlykeeping formability of the fourth lens and maintaining thelow-profileness. When a value is below the upper limit of theconditional expression (3), the thickness on the optical axis of thefourth lens is prevented from being excessively large, and securing airspace on the object side and the image side of the fourth lens isfacilitated. As a result, low-profileness can be maintained. On theother hand, when the value is above the lower limit of the conditionalexpression (3), the thickness on the optical axis of the fourth lens isprevented from being excessively small, and formability of the lens canbe properly kept.

According to the imaging lens comprising the above five opticalelements, it is preferable that aspheric surfaces on both sides of theaberration correction optical element varies its object side and imageside in a direction toward the object side as a distance from the axisincreases. By forming such aspheric surfaces, an angle of light rayemitted from the aberration correction optical element is controlled andaberration of marginal ray can be suppressed. As a result, aberrationcorrection in the peripheral area is facilitated.

According to the imaging lens comprising the above five opticalelements, it is preferable that the aspheric surface having at least onepole point at an off-axial position is formed on the image-side surfaceof the fourth lens.

By forming the aspheric surface having the pole point on the image-sidesurface of the fourth lens, field curvature and distortion can beproperly corrected, and chief ray angle to the image sensor can beproperly controlled.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (4) issatisfied:0.07<TN/f<0.30  (4)

-   where-   f: focal length of the overall optical system, and-   TN: distance along an optical axis of an air space for arranging the    aberration correction optical element.

The conditional expression (4) defines an appropriate arrangement spaceof the aberration correction optical element, and is a condition formaintaining the low-profileness and properly correcting the aberrationsat the in the peripheral area. When a value is below the upper limit ofthe conditional expression (4), the low-profileness can be maintainedand the arrangement space of the aberration correction optical elementcan be secured. On the other hand, when the value is above the lowerlimit of the conditional expression (4), the arrangement space of theaberration correction optical element can be prevented from beingexcessively small. Accordingly, flexibility in a shape of the asphericsurface on the both sides is increased and an effect of the aberrationcorrection by the optical element is also enhanced.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (5) issatisfied:2.4<(TNT/TTL)×100<10.8  (5)

-   where-   TTL: distance along an optical axis from an object-side surface of    the first lens to an image plane, and-   TNT: thickness on the optical axis of the aberration correction    optical element.

The conditional expression (5) defines an appropriate scope of thicknesson the optical axis of the aberration correction optical element, and isa condition for properly keeping formability of the aberrationcorrection optical element and maintaining the low-profileness. When avalue is below the upper limit of the conditional expression (5), thethickness on the optical axis of the aberration correction opticalelement is prevented from being excessively large, and securing airspace on the object side and the image side of the aberration correctionoptical element is facilitated. As a result, low-profileness can bemaintained. On the other hand, when the value is above the lower limitof the conditional expression (5), the thickness on the optical axis ofthe aberration correction optical element is prevented from beingexcessively small, and formability of the lens can be properly kept.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (6) issatisfied:2.00<(d2/TTL)×100<6.5  (6)

-   where-   TTL: distance along an optical axis from an object-side surface of    the first lens to an image plane, and-   d2: thickness on the optical axis of the second lens.

The conditional expression (6) defines an appropriate scope of thicknesson the optical axis of the second lens, and is a condition for properlykeeping formability of the second lens and maintaining thelow-profileness. When a value is below the upper limit of theconditional expression (6), the thickness on the optical axis of thesecond lens is prevented from being excessively large, and securing airspace on the object side and the image side of the second lens isfacilitated. As a result, low-profileness can be maintained. On theother hand, when the value is above the lower limit of the conditionalexpression (6), the thickness on the optical axis of the second lens isprevented from being excessively small, and formability of the lens canbe properly kept.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (7) issatisfied:0.30<f1/1<1.1  (7)

-   where-   f: focal length of the overall optical system, and-   f1: focal length of the first lens.

The conditional expression (7) defines refractive power of the firstlens, and is a condition for achieving the low-profileness and theproper aberration correction. When a value is below the upper limit ofthe conditional expression (7), positive refractive power of the firstlens becomes appropriate, and low-profileness is facilitated. On theother hand, when the value is above the lower limit of the conditionalexpression (7), high-order spherical aberration and the coma aberrationcan be suppressed to be small.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (8) issatisfied:−0.01<r1/r2<0.6  (8)

-   where-   r1: curvature radius of the object-side surface of the first lens,    and-   r2: curvature radius of the image-side surface of the first lens.

The conditional expression (8) defines relationship of the curvatureradii of the object-side surface and the image-side surface of the firstlens, and is a condition for suppressing occurrence of the sphericalaberration. When a value is below the upper limit of the conditionalexpression (8), the positive refractive power of the first lens ismaintained and the low-profileness is facilitated. On the other hand,when the value is above the lower limit of the conditional expression(8), the positive refractive power of the object-side surface of thefirst lens is prevented from being excessively large, and occurrence ofthe spherical aberration is suppressed. Additionally, sensitivity tomanufacturing error is reduced.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (9) issatisfied:−1.6<f2/f<−0.6  (9)

-   where-   f: focal length of the overall optical system, and-   f2: focal length of the second lens.

The conditional expression (9) defines the refractive power of thesecond lens, and is a condition for achieving the low-profileness andthe proper aberration correction. When a value is below the upper limitof the conditional expression (9), negative refractive power of thesecond lens becomes appropriate, and low-profileness is facilitated. Onthe other hand, when the value is above the lower limit of theconditional expression (9), correction of the spherical aberration andthe chromatic aberration occurred at the first lens is facilitated.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (10) issatisfied:1.5<r3/r4<5.0  (10)

-   where-   r3: curvature radius of the object-side surface of the second lens,    and-   r4: curvature radius of the image-side surface of the second lens.

The conditional expression (10) defines relationship of the curvatureradii of the object-side surface and the image-side surface of thesecond lens, and is a condition for suppressing occurrence of theastigmatism. By satisfying the conditional expression (10), the secondlens becomes a meniscus lens near the optical axis, and the astigmatismcan be properly corrected.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (11) issatisfied:0.5<|f3|/f<3.4  (11)

-   where-   f: focal length of the overall optical system, and-   f3: focal length of the third lens.

The conditional expression (11) defines the refractive power of thethird lens, and is a condition for achieving the proper aberrationcorrection. By satisfying the conditional expression (11), positive ornegative refractive power of the third lens becomes appropriate, and itis facilitated to suppress the high-order spherical aberration and thecoma aberration to be small.

According to the imaging lens comprising the above five opticalelements, composite focal length of the second lens and the third lensis preferably negative, and it is further preferable that a belowconditional expression (12) is satisfied:−9.6<f23/f<−0.25  (12)

-   where-   f: focal length of the overall optical system, and-   f23: composite focal length of the second lens and the third lens.

The conditional expression (12) defines an appropriate scope of thecomposite focal length of the second lens and the third lens, and is acondition for the low-profileness and the proper aberration correction.When a value is below the upper limit of the conditional expression(12), negative composite refractive power of the second lens and thethird lens becomes appropriate, and the low-profileness of the imaginglens is facilitated. On the other hand, when the value is above thelower limit of the conditional expression (12), correction of the fieldcurvature and the chromatic aberration is facilitated.

According to the imaging lens comprising the above five opticalelements, it is preferable that the fourth lens has a meniscus shapenear the optical axis.

Thus the fourth lens has the meniscus shape near the optical axis, themore proper correction of the field curvature is enabled.

According to the imaging lens comprising the above five opticalelements, it is preferable that a below conditional expression (13) issatisfied:0.5<r7/r8<2.10  (13)

-   where-   r7: curvature radius of the object-side surface of the fourth lens,    and-   r8: curvature radius of the image-side surface of the fourth lens.

The conditional expression (13) defines relationship of the curvatureradii of the object-side surface and the image-side surface of thefourth lens, and is a condition for properly correcting the sphericalaberration, maintaining the low-profileness, and relaxing thesensitivity to manufacturing error. When a value is below the upperlimit of the conditional expression (13), the refractive power of aconcave surface of the image side of the fourth lens becomesappropriate, and the spherical aberration occurred at this surface issuppressed and the sensitivity to manufacturing error is reduced. On theother hand, when the value is above the lower limit of the conditionalexpression (13), positive or negative refractive power of the fourthlens becomes appropriate, the low-profileness is enabled.

According to the imaging lens comprising the above five opticalelements, it is preferable that at least one surface of the first lens,the second lens, the third lens and the fourth lens, respectively is theaspheric surface. Using the aspheric surface enables the propercorrection of the aberrations.

Effect of Invention

According to the present invention, there can be provided an imaginglens having small ratio of the total track length to the focal length ofan overall optical system and the high resolution by reducing telephotoratio.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a general configuration of an imaginglens in Example 1 according to the present invention;

FIG. 2 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 1 according to the present invention;

FIG. 3 is a schematic view showing the general configuration of animaging lens in Example 2 according to the present invention;

FIG. 4 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 2 according to the present invention;

FIG. 5 is a schematic view showing the general configuration of animaging lens in Example 3 according to the present invention;

FIG. 6 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 3 according to the present invention;

FIG. 7 is a schematic view showing the general configuration of animaging lens in Example 4 according to the present invention;

FIG. 8 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 4 according to the present invention.

FIG. 9 is a schematic view showing a general configuration of an imaginglens in Example 5 according to the present invention;

FIG. 10 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 5 according to the present invention;

FIG. 11 is a schematic view showing the general configuration of animaging lens in Example 6 according to the present invention;

FIG. 12 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 6 according to the present invention;

FIG. 13 is a schematic view showing the general configuration of animaging lens in Example 7 according to the present invention;

FIG. 14 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 7 according to the present invention;

FIG. 15 is a schematic view showing the general configuration of animaging lens in Example 8 according to the present invention;

FIG. 16 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 8 according to the present invention.

FIG. 17 is a schematic view showing the general configuration of animaging lens in Example 9 according to the present invention;

FIG. 18 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 9 according to the present invention.

FIG. 19 is a schematic view showing the general configuration of animaging lens in Example 10 according to the present invention;

FIG. 20 shows spherical aberration, astigmatism, and distortion of theimaging lens in Example 10 according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the preferred embodiment of the present invention will bedescribed in detail referring to the accompanying drawings.

FIGS. 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19 are schematic views showingthe general configurations of the imaging lenses in Examples 1 to 10according to the embodiments of the present invention, respectively.Since all FIGS. 1, 3, 5, 7, 9, 11, 13, 15 and 17 have the same basiclens configuration, the general configuration of an imaging lensaccording to this embodiment is explained below mainly referring to theschematic view of Example 1.

FIG. 1 shows the configuration of the imaging lens according to theExample 1, and an optical axis (AX) is a center line of optical path ofthe light entering from an object side. As shown in FIG. 1 , an imaginglens according to this embodiment comprises, in order from an objectside to an image side, a first lens L1 as a first optical element havingpositive refractive power, a second lens L2 as a second optical elementhaving negative refractive power and a convex surface facing the objectside near an optical axis AX, a third lens L3 as a third opticalelement, and a fourth lens L4 as a fourth optical element having convexsurface facing the object surface near the optical axis AX, and anaberration correction optical element NE as a fifth optical elementhaving flat and aspheric surfaces near the optical axis AX is arrangedbetween the third lens L3 and the fourth lens L4. Therefore, the imaginglens according to this embodiment is composed of five optical elements,four optical elements having the refractive power and one aberrationcorrection optical element having no substantial refractive power.

The aberration correction optical element NE having no substantialrefractive power which is arranged in the above embodiment has a shapeof a parallel plate near the optical axis AX. Therefore, it has noinfluence upon the refractive power of an overall optical system of theimaging lens or upon the refractive power of the four lenses from thefirst lens L1 as the first optical element to the fourth lens L4 as thefourth optical element. So, aberrations only in a peripheral area arecorrected without changing parameters such as the focal length of theoverall optical system, thickness at a center of the lens, and so on.

A filter IR such as an IR cut filter and a cover glass is locatedbetween the fourth lens L4 and an image plane IMG (namely, the imageplane of the imaging lens). The filter IR is omissible.

In each Example, there are many options such that the refractive powerof the third lens L3 and the fourth lens L4 may be positive or negative,and an image-side surface of the first lens L1 and an object-side andimage-side surfaces of the third lens L3 may be convex or concave nearthe optical axis AX. In each Example, the most suitable combination isselected for achieving desirable performance.

More specifically, refractive power arrangement in the Examples 1 to 3is, in order from the object side, +−+−, the refractive powerarrangement in the Examples 4, 6 and 7 is, in order from the objectside, +−−+, and the refractive power arrangement in the Examples 5, 8and 9 is, in order from the object side, +−−−. Features that the firstlens L1 has the positive refractive power and the second lens L2 has thenegative refractive power are common to all of Examples. Regarding theshape of the lens, the object-side surface of the first lens L1 isconvex near the optical axis AX, the second lens is a meniscus lenshaving the convex object-side surface near the optical axis AX, and thefourth lens L4 is a meniscus lens having the convex object-side surfacenear the optical axis AX. These features are common to all of theExamples. Such combination of the refractive power and the shape of thesurface is only one example, and various combinations may be selectedaccording to a system to which the lenses are adopted without beingcontrary to an object of the present invention.

An Example 10 as shown in FIG. 19 shows an embodiment in which a prismPR is added on the object side of the imaging lens comprising the fiveoptical elements of the Example 8. An inclined surface of the prism PRfunctions as a refractive surface for bending an optical path at anapproximately right angle. Since the imaging lens comprising the fiveoptical elements according to the present invention is a telephoto typeoptical system having a telephoto ratio of less than 1.0, total tracklength is longer than that of an optical system of wide field of viewtype. If a folded optics to which the prism PR is added closest to theobject side and the optical path is bend at the approximately rightangle is used, as shown in FIG. 19 , the imaging lens can be alsomounted in a thin device by rotating arrangement of the imaging lens by90°. If a material having a large refractive index is used for the prismPR, the prism PR itself becomes compact, and is easily adopted to thethin device. Furthermore, by using the flat surface for the refractivesurface of the prism PR, occurrence of asymmetric distortion and fieldcurvature can be suppressed. In place of the prism PR, a reflector canbe used for the folded optics and configuration of the folded optics isflexible if the optical path is folded at an approximately right angle.

The imaging lens comprising the five optical elements according to thepresent embodiments facilitates manufacture by using plastic materialsto all of the lenses, and realizes mass production in a low cost.Additionally, both surfaces of all of the lenses are made as properaspheric surfaces, and the aberrations are favorably corrected.

The material applied to the lens is not limited to the plastic material.By using glass material, further high performance may be aimed. All ofsurfaces of lenses are preferably formed as aspheric surfaces, however,spherical surfaces may be adopted which is easy to manufacture inaccordance with required performance.

The imaging lens according to the present embodiments shows preferableeffect by satisfying the below conditional expressions (1) to (13).0.55<TTL/f<1.00  (1)2.00<(d3/TTL)×100<12.65  (2)2.00<(d4/TTL)×100<7.10  (3)0.07<TN/f<0.30  (4)2.4<(TNT/TTL)×100<10.8  (5)2.00<(d2/TTL)×100<6.5  (6)0.30<f1/1<1.1  (7)−0.01<r1/r2<0.6  (8)−1.6<f2/f<−0.6  (9)1.5<r3/r4<5.0  (10)0.5<|f3|/f<3.4  (11)−9.6<f23/f<−0.25  (12)0.5<r7/r8<2.10  (13)

-   -   where    -   f: focal length of the overall optical system,    -   TTL: distance along an optical axis AX from an object-side        surface of the first lens L1 to an image plane IMG,    -   d2: thickness on the optical axis of the second lens L2,    -   d3: thickness on the optical axis of the third lens L3,    -   d4: thickness on the optical axis of the fourth lens L4,    -   TNT: thickness on the optical axis AX of the aberration        correction optical element NE,    -   TN: distance along an optical axis AX of an air space for        arranging the aberration correction optical element NE,    -   f1: focal length of the first lens L1,    -   f2: focal length of the second lens L2,    -   f3: focal length of the third lens L3,    -   f23: composite focal length of the second lens L2 and the third        lens L3,    -   r1: curvature radius of the object-side surface of the first        lens L1,    -   r2: curvature radius of the image-side surface of the first lens        L1,    -   r3: curvature radius of the object-side surface of the second        lens L2,    -   r4: curvature radius of the image-side surface of the second        lens L2,    -   r7: curvature radius of the object-side surface of the fourth        lens L3, and    -   r8: curvature radius of the image-side surface of the fourth        lens L3.

It is not necessary to satisfy the above all conditional expressions,and by satisfying the conditional expression individually, operationaladvantage corresponding to each conditional expression can be obtained.

The imaging lens according to the present embodiments shows furtherpreferable effect by satisfying the below conditional expressions (1a)to (13a).0.71<TTL/f<1.00  (1a)2.51<(d3/TTL)×100<11.16  (2a)2.41<(d4/TTL)×100<6.22  (3a)0.09<TN/f<0.26  (4a)2.97<(TNT/TTL)×100<9.51  (5a)2.53<(d2/TTL)×100<5.67  (6a)0.36<f1/1<0.91  (7a)−0.005<r1/r2<0.477  (8a)−1.3542/k−0.74  (9a)1.87<r3/r4<4.40  (10a)0.61<|f3|/f<2.94  (11a)−8.45<f23/f<−0.36  (12a)0.70<r7/r8<1.81  (13a)

The signs in the above conditional expressions have the same meanings asthose in the paragraph before the preceding paragraph.

In this embodiment, the aspheric shapes of the surfaces of the asphericlens are expressed by Equation 1, where Z denotes an axis in the opticalaxis direction, H denotes a height perpendicular to the optical axis, Rdenotes a curvature radius, k denotes a conic constant, and A4, A6, A8,A10, A12, A14, and A16 denote aspheric surface coefficients.

$\begin{matrix}{Z = {\frac{\frac{H^{2}}{R}}{1 + \sqrt{1 - {( {k + 1} )\frac{H^{2}}{R^{2}}}}} + {A_{4}H^{4}} + {A_{6}H^{6}} + {A_{8}H^{8}} + {A_{10}H^{10}} + {A_{12}H^{12}} + {A_{14}H^{14}} + {A_{16}H^{16}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Next, examples of the imaging lens according to this embodiment will beexplained. In each example, f denotes the focal length of the overalloptical system of the imaging lens, Fno denotes an F-number, ω denotes ahalf field of view, and ih denotes a maximum image height. Additionally,i denotes surface number counted from the object side, r denotes acurvature radius, d denotes the distance of lenses along the opticalaxis (surface distance), Nd denotes a refractive index at d-ray(reference wavelength), and vd denotes an abbe number at d-ray. As foraspheric surfaces, an asterisk (*) is added after surface number i.

Example 1

The basic lens data is shown below in Table 1.

TABLE 1 Example 1 Unit mm f = 10.35 Fno = 2.8 ω(°) = 14.9 ih = 2.62 TTL= 9.88 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number vd ( Object ) Infinity Infinity  1 (Stop ) Infinity −0.5173  2* 2.8030 0.8669 1.544 55.86  3* 6.7578 0.1046 4* 11.7546 0.3514 1.650 21.54  5* 4.5076 0.8248  6* 2.8696 0.9271 1.53555.66  7* 4.3031 0.8436  8* Infinity 0.4974 1.650 21.54  9* Infinity0.6292 10* 3.9553 0.5342 1.535 55.66 11* 2.7041 0.5000 12 Infinity0.2100 1.517 64.20 13 Infinity 3.6643 Image Plane Infinity ConstituentLens Data Lens Start Surface Focal Length Composite Focal Length 1 28.168 f12 20.175 2 4 −11.461 f23 −76.047 3 6 13.145 f34 24.251 4 10−18.777 Aspheric Surface Data Second Surface Third Surface FourthSurface Fifth Surface Sixth Surface k   0.000000E+00   0.000000E+00  0.000000E+00 −6.070000E+00   0.000000E+00 A4 −5.273323E−03−1.563722E−02 −8.122403E−03   1.085686E−03 −1.758940E−02 A6−1.072083E−03   1.214402E−03   5.626665E−03   2.850243E−03 −3.594036E−03A8 −3.064622E−04 −2.630533E−04 −9.033017E−04   1.735028E−04  2.227164E−03 A10   0.000000E+00 −3.156556E−05   0.000000E+00−1.075789E−04 −2.815564E−04 A12   0.000000E+00   7.253542E−06  0.000000E+00 −1.871580E−05   3.279344E−04 A14   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 −1.226767E−04 A16  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  1.437481E−05 Seventh Surface Eighth Surface Ninth Surface TenthSurface Eleventh Surface k   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00 −9.000000E+00 A4 −1.287138E−02 −2.753038E−02−7.559557E−02 −2.161895E−01 −1.261448E−01 A6 −2.579278E−03  3.016120E−02   7.741048E−02   7.808294E−02   6.438565E−02 A8−1.825874E−03 −1.140848E−02 −4.195589E−02 −1.971080E−03 −2.411793E−02A10   2.963604E−03 −5.161968E−03   1.227744E−02 −2.010638E−02  4.702607E−03 A12 −9.586110E−04   5.528321E−03 −2.369911E−03  1.084291E−02 −4.370171E−05 A14   1.262241E−04 −1.997011E−03  1.970815E−04 −2.442818E−03 −1.359987E−04 A16   0.000000E+00  2.599796E−04   1.585783E−05   2.209336E−04   1.594514E−05

The imaging lens in Example 1 satisfies conditional expressions (1) to(13) as shown in Table 11.

FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 1. The spherical aberration diagramshows the amount of aberration at wavelengths of F-ray (486 nm), d-ray(588 nm), and C-ray (656 nm). The astigmatism diagram shows the amountof aberration at d-ray on a sagittal image surface S and on tangentialimage surface T, respectively (same as FIGS. 4, 6, 8, 10, 12, 14, 16, 18and 20 ). As shown in FIG. 2 , each aberration is corrected excellently.

Example 2

The basic lens data is shown below in Table 2.

TABLE 2 Example 2 Unit mm f = 10.36 Fno = 2.8 ω(°) = 14.0 ih = 2.62 TTL= 9.87 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number vd ( Object ) Infinity Infinity  1 (Stop ) Infinity −0.5767  2* 2.7151 0.9046 1.544 55.86  3* 8.0972 0.0800 4* 21.2320 0.3519 1.650 21.54  5* 5.6664 0.4035  6* 8.7547 0.9331 1.53555.66  7* −250.0000 0.9944  8* Infinity 0.8161 1.650 21.54  9* Infinity0.5567 10* 3.6258 0.5000 1.535 55.66 11* 2.3000 0.5000 12 Infinity0.2100 1.517 64.20 13 Infinity 3.6952 Image Plane Infinity ConstituentLens Data Lens Start Surface Focal Length Composite Focal Length 1 27.085 f12 13.900 2 4 −11.992 f23 −54.281 3 6 15.836 f34 157.173 4 10−13.541 Aspheric Surface Data Second Surface Third Surface FourthSurface Fifth Surface Sixth Surface k   0.000000E+00   0.000000E+00  0.000000E+00 −6.100000E+00   0.000000E+00 A4 −3.449959E−03−1.296672E−02 −7.811511E−03   2.136514E−04 −1.133403E−02 A6−4.656948E−04   1.892955E−03   5.955009E−03   2.895464E−03 −5.169090E−03A8 −4.701318E−04 −1.969583E−04 −7.384022E−04 −9.041529E−05  6.881001E−03 A10   0.000000E+00 −2.815283E−05   0.000000E+00  6.102173E−06 −3.954930E−03 A12   0.000000E+00   1.425558E−06  0.000000E+00   2.836449E−06   1.606323E−03 A14   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 −3.585033E−04 A16  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  3.083024E−05 Seventh Surface Eighth Surface Ninth Surface TenthSurface Eleventh Surface k   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00 −9.000000E+00 A4 −1.048890E−02 −2.306851E−02−7.064492E−02 −2.295393E−01 −1.072794E−01 A6 −5.220221E−05  1.675491E−02   6.574254E−02   9.685049E−02   4.596451E−02 A8  1.615051E−03 −4.776549E−03 −3.929374E−02 −1.251478E−02 −1.607162E−03A10 −1.016523E−03 −4.059341E−03   1.921431E−02 −8.287726E−03−1.044181E−02 A12   1.243594E−04   3.372597E−03 −9.097633E−03  1.175042E−03   5.411458E−03 A14 −1.001792E−08 −1.454847E−03  2.589834E−03   1.148805E−03 −1.127756E−03 A16   0.000000E+00  2.421220E−04 −2.866331E−04 −2.672647E−04   8.677205E−05

The imaging lens in Example 2 satisfies conditional expressions (1) to(13) as shown in Table 11.

FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 2. As shown in FIG. 4 , eachaberration is corrected excellently.

Example 3

The basic lens data is shown below in Table 3.

TABLE 3 Example 3 Unit mm f = 10.35 Fno = 2.8 ω(°) = 14.2 ih = 2.62 TTL= 9.88 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number vd ( Object ) Infinity Infinity  1Infinity Infinity  2* 2.8345 0.8670 1.544 55.86  3* 7.2677 0.1244  4 (Stop ) Infinity −0.0050  5* 12.4155 0.3503 1.650 21.54  6* 4.6170 0.8453 7* 2.9148 0.9584 1.535 55.66  8* 4.2009 0.8384 9* Infinity 0.5009 1.65021.54 10* Infinity 0.5410 11* 3.9097 0.5312 1.535 55.66 12* 2.70000.5000 13 Infinity 0.2100 1.517 64.20 14 Infinity 3.5928 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length CompositeFocal Length 1 2 7.987 f12 18.971 2 5 −11.505 f23 −53.669 3 7 14.129 f3427.618 4 11 −19.264 Aspheric Surface Data Second Surface Third SurfaceFifth Surface Sixth Surface Seventh Surface k   0.000000E+00  0.000000E+00   0.000000E+00 −6.0740000E+00   0.000000E+00 A4−5.234178E−03 −1.543855E−02 −7.997102E−03   8.492032E−04 −1.841052E−02A6 −1.079193E−03   1.262156E−03   5.641456E−03   2.716705E−03−1.674020E−03 A8 −3.010493E−04 −2.766078E−04 −9.305445E−04  1.457414E−04 −8.830697E−04 A10   0.000000E+00 −3.490244E−05  0.000000E+00 −9.502757E−05   2.179098E−03 A12   0.000000E+00  7.600526E−06   0.000000E+00 −1.909259E−05 −6.942794E−04 A14  0.000000E+00   0.000000E+00   0.000000E+00   0.000000E+00  9.278647E−05 A16   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00 −3.629464E−06 Eighth Surface Ninth Surface Tenth SurfaceEleventh Surface Twelfth Surface k   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00 −9.000000E+00 A4 −1.469858E−02−2.964626E−02 −7.936413E−02 −2.210627E−01 −1.238394E−01 A6 −2.415821E−04  3.009286E−02   8.158646E−02   8.061372E−02   6.613291E−02 A8−5.140643E−03 −6.159835E−03 −4.377096E−02 −5.811941E−04 −2.259344E−02A10   5.780603E−03 −1.093386E−02   1.492036E−02 −1.931688E−02  3.056249E−03 A12 −2.130517E−03   8.789974E−03 −4.856856E−03  8.616925E−03   5.530597E−04 A14   3.145809E−04 −3.121085E−03  1.081020E−03 −1.365524E−03 −2.234826E−04 A16   0.000000E+00  4.297570E−04 −9.101200E−05   5.7726931E−05   1.930696E−05

The imaging lens in Example 3 satisfies conditional expressions (1) to(13) as shown in Table 11.

FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 3. As shown in FIG. 6 , eachaberration is corrected excellently.

Example 4

The basic lens data is shown below in Table 4.

TABLE 4 Example 4 Unit mm f = 9.90 Fno = 2.6 ω(°) = 14.6 ih = 2.62 TTL =8.90 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number vd ( Object ) Infinity Infinity  1Infinity Infinity  2* 2.5308 1.1340 1.544 55.86  3* −2069.0280 0.0975  4( Stop ) Infinity 0.0047  5* 17.3664 0.4390 1.661 20.37  6* 4.54321.3411  7* 4.6866 0.3000 1.535 55.66  8* 2.5030 0.9396  9* Infinity0.4282 1.661 20.37 10* Infinity 0.1304 11* 2.9368 0.3263 1.535 55.66 12*3.2383 0.3000 13 Infinity 0.2100 1.517 64.20 14 Infinity 3.3217 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal LengthComposite Focal Length 1 2 4.645 f12 7.315 2 5 −9.441 f23 −4595 3 7−10.550 f34 −13.823 4 11 42.822 Aspheric Surface Data Second SurfaceThird Surface Fifth Surface Sixth Surface Seventh Surface k  0.000000E+00   0.000000E+00   0.000000E+00 −6.080000E+00  0.000000E+00 A4 −4.107324E−04 −7.557835E−03 −1.848474E−02−5.114836E−03 −1.254475E−01 AS   2.805118E−05   3.586297E−03  1.681657E−02   2.319237E−02   1.006195E−01 A8 −4.668923E−04−2.452053E−04 −4.109219E−03 −9.474571E−03 −1.503095E−02 A10  8.151119E−05 −2.706636E−05   4.807371E−04   3.843876E−03 −2.213184E−02A12   0.000000E+00 −3.373375E−06 −5.734298E−05 −1.406831E−03  1.726926E−02 A14   0.000000E+00   6.170776E−08   0.000000E+00  2.416671E−04 −5.044697E−03 A16   0.000000E+00   0.000000E+00  0.000000E+00 −1.705040E−05   4.887430E−04 Eighth Surface Ninth SurfaceTenth Surface Eleventh Surface Twelfth Surface k   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 −9.000000E+00 A4−1.630424E−01 −6.627008E−02 −2.146244E−01 −3.996676E−01 −1.758609E−01 A6  1.333784E−01   1.572419E−03   2.515114E−01   3.707728E−01  1.183279E−01 A8 −4.349255E−02   5.137366E−02 −1.804595E−01−2.364812E−01 −6.281345E−02 A10 −2.453462E−03 −7.350033E−02  7.041214E−02   8.748925E−02   2.075816E−02 A12   8.650524E−03  4.442658E−02 −1.508759E−02 −1.784329E−02 −3.906984E−03 A14−2.113240E−03 −1.348266E−02   1.554788E−03   1.892217E−03   3.668059E−04A16   0.000000E+00   1.716118E−03 −3.255704E−05 −8.357740E−05−1.169629E−05

The imaging lens in Example 4 satisfies conditional expressions (1) to(13) as shown in Table 11.

FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion(%) of the imaging lens in Example 4. As shown in FIG. 8 , eachaberration is corrected excellently.

Example 5

The basic lens data is shown below in Table 5.

TABLE 5 Example 5 Unit mm f = 12.00 Fno = 2.8 ω(°) = 12.3 ih = 2.62 TTL= 10.18 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number vd ( Object ) Infinity Infinity  1Infinity Infinity  2* 2.7573 1.3000 1.544 55.86  3* 407.4974 0.1390  4 (Stop ) Infinity −0.1160  5* 17.3402 0.3300 1.661 20.37  6* 4.8939 1.7763 7* 5.4053 0.3000 1.535 55.66  8* 3.3403 0.9569  9* Infinity 0.43971.661 20.37 10* Infinity 0.0500 11* 10.9519 0.3000 1.535 55.66 12*7.0499 0.5000 13 Infinity 0.2100 1.517 64.20 14 Infinity 4.0646 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal LengthComposite Focal Length 1 2 5.094 f12 8.194 2 5 −10.429 f23 −6.009 3 7−17.220 f34 −11.538 4 11 −38.016 Aspheric Surface Data Second SurfaceThird Surface Fifth Surface Sixth Surface Seventh Surface k  0.000000E+00   0.000000E+00   0.000000E+00 −6.060000E+00  0.000000E+00 A4 −4.287561E−05 −8.336338E−04 −1.295548E−02−7.899859E−03 −4.239411E−02 A6   2.168369E−04   1.581347E−03  9.218452E−03   1.726469E−02   8.160367E−03 A8 −1.194331E−04−1.335636E−04 −1.652884E−03 −1.000932E−02   5.503224E−02 A10  1.440273E−06 −2.312744E−05   1.488785E−04   5.562852E−03 −6.600477E−02A12   0.000000E+00 −6.820433E−07 −1.207766E−05 −1.98,4591E−03  3.614931E−02 A14   0.000000E+00   4.405095E−07   0.000000E+00  3.800608E−04 −9.565310E−03 A16   0.000000E+00   0.000000E+00  0.000000E+00 −3.105163E−05   9.657739E−04 Eighth Surface Ninth SurfaceTenth Surface Eleventh Surface Twelfth Surface k   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 −9.000000E+00 A4−6.994229E−02 −5.642827E−02 −3.067394E−01 −4.267998E−01 −1.027730E−01 A6  5.666739E−02   9.534037E−03   5.933960E−01   7.878634E−01  9.661222E−02 A8 −6.116596E−03   2.030091E−02 −6.779832E−01−8.823656E−01 −8.212454E−02 A10 −1.687960E−02 −4.940992E−02  4.333873E−01   5.829211E−01   5.128394E−02 A12   1.182567E−02  2.855856E−02 −1.599873E−01 −2.224258E−01 −1.972570E−02 A14−2.241556E−03 −6.033268E−03   3.200299E−02   4.515926E−02   3.996862E−03A16   0.000000E+00   3.804451E−04 −2.674820E−03 −3.762493E−03−3.240814E−04

The imaging lens in Example 5 satisfies conditional expressions (1) to(13) as shown in Table 11.

FIG. 10 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 5. As shown in FIG. 10 ,each aberration is corrected excellently.

Example 6

The basic lens data is shown below in Table 6.

TABLE 6 Example 6 Unit mm f = 12.00 Fno = 2.8 ω(°) = 12.5 ih = 2.62 TTL= 10.07 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number vd ( Object ) Infinity Infinity  1Infinity Infinity  2* 2.6101 1.3090 1.553 71.68  3* 21.6890 0.2171  4 (Stop ) Infinity −0.1741  5* 11.0124 0.3000 1.661 20.37  6* 5.0186 1.7098 7* −13.0628 0.3000 1.535 55.66  8* 7.2164 0.7491  9* Infinity 0.41161.661 20.37 10* Infinity 0.0500 11* 10.8284 0.3000 1.535 55.66 12*13.1968 0.5000 13 Infinity 0.2100 1.517 64.20 14 Infinity 4.2580 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal LengthComposite Focal Length 1 2 5.235 f12 7.222 2 5 −14.238 f23 −5.012 3 7−8.647 f34 −9.424 4 11 108.046 Aspheric Surface Data Second SurfaceThird Surface Fifth Surface Sixth Surface Seventh Surface k  0.000000E+00   0.000000E+00   0.000000E+00 −6.080000E+00  0.000000E+00 A4   1.924316E−04 −1.147623E−03 −1.905004E−02−1.756461E−02 −6.738738E−02 A6 −1.684336E−04   1.461546E−03  1.736622E−02   2.976244E−02   4.100722E−02 A8 −5.793915E−05−1.322531E−04 −5.349500E−03 −1.749609E−02   8.067919E−02 A10−2.453470E−06 −1.703886E−05   9.817000E−04   8.391846E−03 −1.399091E−01A12   0.000000E+00 −8.996783E−08 −9.245059E−05 −2.773491E−03  9.078:331E−02 A14   0.000000E+00 −2.614900E−08   0.000000E+00  5.313835E−04 −2.749752E−02 A16   0.000000E+00   0.000000E+00  0.000000E+00 −4.593963E−05   3.187747E−03 Eighth Surface Ninth SurfaceTenth Surface Eleventh Surface Twelfth Surface k   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 −9.000000E+00 A4−1.095502E−01 −8.571128E−02 −3.135403E−01 −3.907639E−01 −8.212220E−02 A6  1.631097E−01   7.132122E−02   5.431480E−01   6.412870E−01  5.440330E−02 A8 −9.332872E−02 −1.477621E−03 −4.907970E−01−6.255188E−01 −4.645210E−02 A10   1.638625E−02 −5.887492E−02  2.262353E−01   3.673216E−01   3.891956E−02 A12   5.871895E−03  3.197182E−02 −5.351967E−02 −1.256184E−01 −1.815730E−02 A14−1.844373E−03 −5.106155E−03   5.329476E−03   2.301281E−02   4.086032E−03A16   0.000000E+00   1.356969E−04 −2.083138E−05 −1.741061E−03−3.517601E−04

The imaging lens in Example 6 satisfies conditional expressions (1) to(13) as shown in Table 11.

FIG. 12 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 6. As shown in FIG. 12 ,each aberration is corrected excellently.

Example 7

The basic lens data is shown below in Table 7.

TABLE 7 Example 7 Unit mm f = 12.00 Fno = 2.8 ω(°) = 12.5 ih = 2.62 TTL= 9.97 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number vd ( Object ) Infinity Infinity  1Infinity Infinity  2* 2.5988 1.3160 1.553 71.68  3* 22.5576 0.2165  4 (Stop ) Infinity −0.1724  5* 11.2633 0.3000 1.661 20.37  6* 5.0332 1.7232 7* −16.6134 0.3000 1.535 55.66  8* 6.5581 0.7588  9* Infinity 0.41821.661 20.37 10* Infinity 0.0500 11* 11.1757 0.3000 1.535 55.66 12*11.6989 0.5000 13 Infinity 0.2100 1.517 64.20 14 Infinity 4.1201 ImagePlane Infinity Constituent Lens Data Lens Start Surface Focal LengthComposite Focal Length 1 2 5.186 f12 7.163 9 5 −14.040 f23 −5.014 3 7−8.752 f34 −8.898 4 11 389.449 Aspheric Surface Data Second SurfaceThird Surface Fifth Surface Sixth Surface Seventh Surface k  0.000000E+00   0.000000E+00   0.000000E+00 −6.060000E+00  0.000000E+00 A4   1.434410E−04 −1.087279E−03 −2.048450E−02−1.874233E−02 −6.282669E−02 A6 −1.870464E−04   1.481661E−03  1.888627E−02   3.057130E−02   2.397201E−02 A8 −6.049370E−05−1.293384E−04 −5.968780E−03 −1.715101E−02   1.134866E−01 A10−2.762434E−06 −1.702788E−05   1.114569E−03   7.847718E−03 −1.743152E−01A12   0.000000E+00 −2.293318E−07 −1.056511E−04 −2.524851E−03  1.105866E−01 A14   0.000000E+00 −8.741376E−08   0.000000E+00  4.765406E−04 −3.346821E−02 A16   0.000000E+00   0.000000E+00  0.000000E+00 −4.134003E−05   3.912551E−03 Eighth Surface Ninth SurfaceTenth Surface Eleventh Surface Twelfth Surface k   0.000000E+00  0.000000E+00   0.000000E+00   0.000000E+00 −9.000000E+00 A4−1.087712E−01 −8.393551E−02 −3.315159E−01 −4.270176E−01 −9.341958E−02 A6  1.642859E−01   7.877161E−02   5.997724E−01   7.255711E−01  7.026835E−02 A8 −9.403562E−02 −2.710897E−02 −5.723663E−01−7.192553E−01 −5.444581E−02 A10   1.692484E−02 −3.144692E−02  2.862533E−01   4.264328E−01   4.016551E−02 A12   5.545004E−03  1.807658E−02 −7.702218E−02 −1.468955E−01 −1.790453E−02 A14−1.814042E−03 −1.680778E−03   9.995180E−03   2.708110E−02   3.988995E−03A16   0.000000E+00 −1.945994E−04 −3.901168E−04 −2.061903E−03−3.445289E−04

The imaging lens in Example 7 satisfies conditional expressions (1) to(13) as shown in Table 11.

FIG. 14 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 7. As shown in FIG. 14 ,each aberration is corrected excellently.

Example 8

The basic lens data is shown below in Table 8.

TABLE 8 Example 8 Unit mm f = 12.00 Fno = 2.6 ω(°) = 12.5 ih = 2.62 TTL= 10.57 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number vd ( Object ) Infinity Infinity  1Infinity Infinity  2* 2.8946 1.3050 1.544 55.86  3* 28.4522 0.1973  4 (Stop ) Infinity −0.1634  5* 15.3702 0.3321 1.661 20.37  6* 4.9478 1.4770 7* 4.0881 0.7572 1.535 55.66  8* 3.0544 1.0120  9* Infinity 0.36881.661 20.37 10* Infinity 0.0641 11* 6.0643 0.3000 1.535 55.66 12* 4.93520.7880 13 Infinity 0.2100 1.517 64.20 14 Infinity 3.9956 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length CompositeFocal Length 1 2 5.816 f12 9.817 2 5 −11.185 f23 −7.453 3 7 −30.329 f34−19.387 4 11 −54.621 Aspheric Surface Data Second Surface Third SurfaceFifth Surface Sixth Surface Seventh Surface k   0.000000E+00  0.000000E+00   0.000000E+00 −6.050000E+00   0.000000E+00 A4−1.771667E−03 −2.193891E−03 −5.317759E−03 −1.550873E−03 −8.469342E−03 A6  3.195294E−04   1.246537E−03   2.939068E−03   6.027491E−03−1.649764E−02 A8 −1.090329E−04 −1.543791E−04   2.105347E−04−1.346818E−03   3.186224E−02 A10 −9.725341E−06 −1.833102E−05−1.265847E−04   2.345925E−04 −2.148406E−02 A12   0.000000E+00  1.285392E−06   6.159471E−06   8.236647E−05   7.791396E−03 A14  0.000000E+00   1.794405E−07   0.000000E+00 −5.221581E−05 −1.431143E−03A16   0.000000E+00   0.000000E+00   0.000000E+00   5.969376E−06  9.824146E−05 Eighth Surface Ninth Surface Tenth Surface EleventhSurface Twelfth Surface k   0.000000E+00   0.000000E+00   0.000000E+00  0.000000E+00 −9.000000E+00 A4 −4.040501E−02 −8.016024E−02−2.469279E−01 −3.287085E−01 −1.021710E−01 A6   3.020201E−02  2.955546E−02   3.538420E−01   3.987325E−01   3.814934E−02 A8−1.180549E−02   2.642715E−02 −2.969362E−01 −3.033254E−01   1.324256E−03A10   2.866936E−03 −7.639896E−02   1.287777E−01   1.307088E−01−1.158606E−02 A12   1.105435E−03   5.817589E−02 −2.688228E−02−3.164461E−02   5.710189E−03 A14 −4.147172E−04 −1.953787E−02  1.543597E−03   4.061342E−03 −1.170815E−03 A16   0.000000E+00  2.503901E−03   1.824327E−04 −2.167431E−04   8.868237E−05

The imaging lens in Example 8 satisfies conditional expressions (1) to(13) as shown in Table 11.

FIG. 16 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 8. As shown in FIG. 16 ,each aberration is corrected excellently.

Example 9

The basic lens data is shown below in Table 9.

TABLE 9 Example 9 Unit mm f = 12.00 Fno = 2.6 ω(°) = 12.4 ih = 2.62 TTL= 10.54 Surface Data Surface Curvature Surface Refractive Abbe Number iRadius r Distance d Index Nd Number vd ( Object) Infinity Infinity  1Infinity Infinity  2* 3.0100 1.3000 1.544 55.86  3* 64.3847 0.1723  4 (Stop ) Infinity −0.1493  5* 16.4103 0.3317 1.661 20.37  6* 5.2414 1.7822 7* 4.6710 0.6570 1.535 55.66  8* 3.4569 1.0017  9* Infinity 0.39211.661 20.37 10* Infinity 0.0506 11* 7.1949 0.3000 1.535 55.66 12* 5.09570.5000 13 Infinity 0.2100 1.517 64.20 14 Infinity 4.0633 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length CompositeFocal Length 1 2 5.758 f12 9.390 2 5 −11.795 f23 −7.831 3 7 −30.648 f34−16.079 4 11 −34.369 Aspheric Surface Data Second Surface Third SurfaceFifth Surface Sixth Surface Seventh Surface k   0.000000E+00  0.000000E+00   0.000000E+00 −6.060000E+00   0.000000E+00 A4−1.645754E−03 −2.397643E−03   1.949896E−03   6.667911E−03 −3.730951E−03A6   3.334878E−04   1.194930E−03 −3.402100E−03   1.097536E−03−1.337562E−02 A8 −1.123926E−04 −1.706964E−04   2.536343E−03−2.536546E−03   2.071262E−02 A10 −9.534742E−06 −1.841871E−05−5.561909E−04   2.488786E−03 −1.035053E−02 A12   0.000000E+00  1.696436E−06   3.828115E−05 −8.861881E−04   2.655671E−03 A14  0.000000E+00   1.833963E−07   0.000000E+00   1.314407E−04−3.043226E−04 A16   0.000000E+00   0.000000E+00   0.000000E+00−7.143206E−06   3.764424E−06 Eighth Surface Ninth Surface Tenth SurfaceEleventh Surface Twelfth Surface k   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00 −9.000000E+00 A4 −2.707631E−02−6.140554E−02 −2.274131E−01 −3.399072E−01 −1.122620E−01 A6  9.561404E−03   7.594958E−03   3.570964E−01   5.153713E−01  9.699879E−02 A8 −1.623249E−03 −1.991526E−02 −3.970538E−01−5.265244E−01 −7.579951E−02 A10   5.718394E−03   1.814284E−02  2.592511E−01   3.212605E−01   3.756514E−02 A12 −2.752446E−03−5.117449E−03 −9.748865E−02 −1.146055E−01 −1.092058E−02 A14  4.265143E−04 −6.765266E−04   1.936763E−02   2.209945E−02  1.700749E−03 A16   0.000000E+00   3.733183E−04 −1.554972E−03−1.773570E−03 −1.099030E−04

The imaging lens in Example 9 satisfies conditional expressions (1) to(13) as shown in Table 11.

FIG. 18 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 9. As shown in FIG. 18 ,each aberration is corrected excellently.

Example 10

The basic lens data is shown below in Table 10.

TABLE 10 Example 10 Unit mm f = 12.00 Fno = 2.6 ω(°) = 12.5 ih = 2.62TTL = 10.57 Surface Data Surface Curvature Surface Refractive AbbeNumber i Radius r Distance d Index Nd Number vd ( Object ) InfinityInfinity 1 Infinity Infinity 2 Infinity 5.0100 1.901 37.05 3 Infinity0.9800 4* 2.8946 1.3050 1.544 55.86 5* 28.4522 0.1973 6 ( Stop )Infinity −0.1634 7* 15.3702 0.3321 1.661 20.37 8* 4.9478 1.4770 9*4.0881 0.7572 1.535 55.66 10* 3.0544 1.0120 11* Infinity 0.3660 1.66120.37 12* Infinity 0.0641 13* 6.0643 0.3000 1.535 55.66 14* 4.93520.7880 15 Infinity 0.2100 1.517 64.20 16 Infinity 3.9956 Image PlaneInfinity Constituent Lens Data Lens Start Surface Focal Length CompositeFocal Length 1 4 5.816 f12 9.817 2 7 −11.185 f23 −7.453 3 9 −30.329 f34−19.387 4 13 −54.621 Aspheric Surface Data Fourth Surface Fifth SurfaceSeventh Surface Eighth Surface Ninth Surface k   0.000000E+00  0.000000E+00   0.000000E+00 −0.050000E+00   0.000000E+00 A4−1.771667E−03 −2.193891E−03 −5.317759E−03 −1.550873E−03 −8.469342E−02 A6  3.195294E−04   1.246537E−03   2.939068E−03   6.027491E−03−1.649764E−02 A8 −1.090329E−04 −1.543791E−04   2.105347E−04−1.346818E−03   3.186224E−02 A10 −9.725341E−06 −1.833102E−05−1.265847E−04   2.345925E−04 −2.148406E−02 A12   0.000000E+00  1.285392E−06   6.159471E−06   8.236647E−05   7.791396E−03 A14  0.000000E+00   1.794405E−07   0.000000E+00 −5.221581E−05 −1.431143E−03A16   0.000000E+00   0.000000E+00   0.000000E+00   5.969178E−06  9.824146E−05 Tenth Surface Eleventh Surface Twelfth Surface ThirteenthSurface Fourteenth Surface k   0.000000E+00   0.000000E+00  0.000000E+00   0.000000E+00 −9.000000E+00 A4 −4.040501E−02−8.016024E−02 −2.469279E−01 −3.287085E−01 −1.021710E−01 A6  3.020201E−02   2.955546E−02   3.538420E−01   3.987325E−01  3.814934E−02 A8 −1.180549E−02   2.642715E−02 −969362E−01 −3.033254E−01  1.324256E−03 A10   2.866936E−03 −7.639896E−02   1.287777E−01  1.367088E−01 −1.158806E−02 A12   1.105435E−03   5.817589E−02−2.68828E−02 −3.164461E−02   5.710189E−03 A14 −4.147172E−04−1.953787E−02   1.543597E−03   4.061342E−03 −1.170815E−03 A16  0.000000E+00   2.5039901E−03   1.824327E−04 −2.1674431E−04  8.868237E−05

The imaging lens in Example 10 satisfies conditional expressions (1) to(13) as shown in Table 11.

FIG. 20 shows spherical aberration (mm), astigmatism (mm), anddistortion (%) of the imaging lens in Example 10. As shown in FIG. 20 ,each aberration is corrected excellently.

In table 11, values of conditional expressions (1) to (13) related tothe Examples 1 to 10 are shown.

TABLE 11 Conditional Expression Example 1 Example 2 Example 3 Example 4Example 5 Example 6 Example 7 Example 8 Example 9 Example 10  (1) T TL/f 0.95 0.95 0.95 0.90 0.85 0.84 0.83 0.88 0.88 0.88  (2) ( d 3/T T L) * 100 9.38 9.45 9.70 3.37 2.95 2.98 3.01 7.16 6.23 7.16  (3) ( d 4/T TL ) * 100 5.41 5.06 5.38 3.67 2.95 2.98 3.01 2.84 2.85 2.84  (4) T N/f0.19 0.23 0.19 0.15 0.12 0.10 0.10 0.12 0.12 0.12  (5) ( T N T/T T L ) *100 5.03 8.27 5.07 4.81 4.32 4.09 4.20 3.49 3.72 3.49  (6) ( d 2 / T T L) * 100 3.56 3.56 3.55 4.93 3.24 2.98 3.01 3.14 3.15 3.14  (7) f 1/f0.79 0.68 0.77 0.47 0.42 0.44 0.43 0.48 0.48 0.48  (8) r 1/r 2 0.41 0.340.39 −0.001 0.01 0.12 0.12 0.10 0.05 0.10  (9) f 2/f −1.11 −1.16 −1.11−0.95 −0.87 −1.19 1.17 −0.93 −0.98 −0.93 (10) r 3/r 4 2.61 3.75 2.693.82 3.54 2.19 2.24 3.11 3.13 3.11 (11) | f 3 |/f 1.27 1.53 1.37 1.071.43 0.72 0.73 2.53 2.55 2.53 (12) f 2 3/f −7.35 −5.24 −5.19 −0.46 −0.50−0.42 −0.42 −0.62 −0.65 −0.62 (13) r 7/r 8 1.46 1.58 1.45 0.91 1.55 0.820.96 1.23 1.41 1.23

When the imaging lens composed of five optical elements according to thepresent invention is adopted to an imaging device mounted in ansmartphone and mobile phone in which increasingly becomes large inpixels, an information terminal such as a game console, PC and a robot,moreover, a home appliance and an automobile with the camera function,there is realized contribution to reducing telephoto ratio of the cameraand also high performance thereof.

What is claimed is:
 1. An imaging lens comprising five optical elements,which comprise first through fourth lenses in order from an object sideto an image side as follows: a first lens as a first optical elementhaving positive refractive power; a second lens as a second opticalelement having negative refractive power and a convex surface facing theobject side near an optical axis; a third lens as a third opticalelement having the refractive power; and a fourth lens as a fourthoptical element having refractive power and the convex surface facingthe object surface near the optical axis, and further comprise anaberration correction optical element as a fifth optical elementarranged between said third lens and said fourth lens, said aberrationcorrection optical element having both flat surfaces near the opticalaxis and aspheric surfaces, wherein a below conditional expression (1)is satisfied:0.55<TTL/f<1.00  (1) where f: focal length of the overall optical systemof an imaging lens, and TTL: distance along an optical axis from anobject-side surface of the first lens to an image plane.
 2. The imaginglens comprising five optical elements according to claim 1, wherein abelow conditional expression (2) is satisfied:2.00<(d3/TTL)×100<12.65  (2) where TTL: distance along an optical axisfrom an object-side surface of the first lens to an image plane, and d3:thickness on the optical axis of the third lens.
 3. The imaging lenscomprising five optical elements according to claim 1, wherein a belowconditional expression (3) is satisfied:2.00<(d4/TTL)×100<7.10  (3) where TTL: distance along an optical axisfrom an object-side surface of the first lens to an image plane, and d4:thickness on the optical axis of the fourth lens.
 4. The imaging lenscomprising five optical elements according to claim 1, wherein a belowconditional expression (4) is satisfied:0.07<TN/f<0.30  (4) where f: focal length of the overall optical systemof an imaging lens, and TN: distance along an optical axis of an airspace for arranging the aberration correction optical element.
 5. Theimaging lens comprising five optical elements according to claim 1,wherein a below conditional expression (5) is satisfied:2.4<(TNT/TTL)×100<10.8  (5) where TTL: distance along an optical axisfrom an object-side surface of the first lens to an image plane, andTNT: thickness on the optical axis of the aberration correction opticalelement.
 6. The imaging lens comprising five optical elements accordingto claim 1, wherein a below conditional expression (6) is satisfied:2.00<(d2/TTL)×100<6.5  (6) where TTL: distance along an optical axisfrom an object-side surface of the first lens to an image plane, and d2:thickness on the optical axis of the second lens.
 7. The imaging lenscomprising five optical elements according to claim 1, wherein a belowconditional expression (7) is satisfied:0.30<f1/1<1.1  (7) where f: focal length of the overall optical systemof an imaging lens, and f1: focal length of the first lens.
 8. Theimaging lens comprising five optical elements according to claim 1,wherein a below conditional expression (8) is satisfied:−0.01<r1/r2<0.6  (8) where r1: curvature radius of the object-sidesurface of the first lens, and r2: curvature radius of the image-sidesurface of the first lens.
 9. The imaging lens comprising five opticalelements according to claim 1, wherein a below conditional expression(9) is satisfied:−1.6<f2/f<−0.6  (9) where f: focal length of the overall optical systemof an imaging lens, and f2: focal length of the second lens.
 10. Theimaging lens comprising five optical elements according to claim 1,wherein a below conditional expression (10) is satisfied:1.5<r3/r4<5.0  (10) where r3: curvature radius of the object-sidesurface of the second lens, and r4: curvature radius of the image-sidesurface of the second lens.
 11. The imaging lens comprising five opticalelements according to claim 1, wherein a below conditional expression(11) is satisfied:0.5<|f3|/f<3.4  (11) where f: focal length of the overall optical systemof an imaging lens, and f3: focal length of the third lens.
 12. Theimaging lens comprising five optical elements according to claim 1,wherein a below conditional expression (12) is satisfied:−9.6<f23/f<−0.25  (12) where f: focal length of the overall opticalsystem of an imaging lens, and f23: composite focal length of the secondlens and the third lens.
 13. The imaging lens comprising five opticalelements according to claim 1, wherein the fourth lens has a meniscusshape near the optical axis.
 14. The imaging lens comprising fiveoptical elements according to claim 1, wherein a below conditionalexpression (13) is satisfied:0.5<r7/r8<2.10  (13) where r7: curvature radius of the object-sidesurface of the fourth lens, and r8: curvature radius of the image-sidesurface of the fourth lens.
 15. The imaging lens comprising five opticalelements according to claim 1, wherein there is provided a folded opticswhich has a refractive surface at a place nearer to an object than saidfirst lens, and enters light on said first lens by folding a directionof the light traveling of an object on said refractive surface at anapproximately right angle.